Cavity filling biopsy site markers

ABSTRACT

The invention provides materials, devices and methods for marking biopsy sites for a limited time. The biopsy-marking materials are ultrasound-detectable bio-resorbable powders, with powder particles typically between about 20 microns and about 800 microns in maximum dimension, more preferably between about 300 microns and about 500 microns. The powders may be formed of polymeric materials containing cavities sized between about 10 microns and about 500 microns, and may also contain binding agents, anesthetic agents, hemostatic agents, and radiopaque markers. Devices for delivering the powders include tubes configured to contain the powders and to fit within a biopsy cannula, the powders being ejected by action of a syringe. Systems may include a tube containing powder, and a syringe containing sterile saline. The tube may be configured to fit within a biopsy cannula such as a Mammotome® or SenoCor 360™ cannula.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/495,408,filed Jun. 13, 2012, now U.S. Pat. No. 8,626,270, which is acontinuation of application Ser. No. 12/852,286, filed Aug. 6, 2010, nowU.S. Pat. No. 8,219,182, which is a continuation of application Ser. No.10/990,327, filed Nov. 16, 2004, now U.S. Pat. No. 7,792,569, which is acontinuation of application Ser. No. 10/124,757, filed Apr. 16, 2002,now U.S. Pat. No. 6,862,470, which is a continuation-in-part ofapplication Ser. No. 09/717,909, filed Nov. 20, 2000, now U.S. Pat. No.6,725,083, which is a continuation-in-part of application Ser. No.09/343,975, filed Jun. 30, 1999, now U.S. Pat. No. 6,347,241, which is acontinuation-in-part of application Ser. No. 09/241,936, filed Feb. 2,1999, now U.S. Pat. No. 6,161,034, which are all hereby incorporated byreference herein in their entireties and from all of which priority ishereby claimed under 35 U.S.C. § 119(e) and § 120.

FIELD OF THE INVENTION

This invention relates generally to the field of acquisition of tissuefrom a patient, as occurs in a biopsy procedure, in particular to themarking of the site within a body from which a biopsy has been taken.

BACKGROUND OF THE INVENTION

In diagnosing and treating certain medical conditions, it is oftendesirable to perform a biopsy, in which a specimen or sample of tissueis removed for pathological examination, tests and analysis. As isknown, obtaining a tissue sample by biopsy and the subsequentexamination are typically employed in the diagnosis of cancers and othermalignant tumors, or to confirm that a suspected lesion or tumor is notmalignant. The information obtained from these diagnostic tests and/orexaminations is frequently used to devise a plan for the appropriatesurgical procedure or other course of treatment. For example, breastbiopsies may be taken where a suspicious lump or swelling is noticed ina breast. Examination of tissue samples taken by biopsy is of particularsignificance in the diagnosis and treatment of breast cancer. In theensuing discussion, the biopsy and treatment site described willgenerally be the human breast, although the invention is suitable formarking biopsy sites in other parts of the human and other mammalianbody as well.

After the biopsy sample is taken, it may take several days or weeksbefore the results of the examination of the sample are obtained, andstill longer before an appropriate treatment decision is reached. If thedecision involves surgery it is clearly important for the surgeon tofind the location in the breast from where the tumor tissue has beentaken in the biopsy procedure, so that the entire tumor and possiblysurrounding healthy tissue can be removed.

However, radiographically imageable tissue features, originally detectedin a mammogram, may be removed, altered or obscured by the biopsyprocedure. In order for the surgeon or radiation oncologist to directsurgical or radiation treatment to the precise location of the breastlesion several days or weeks after the biopsy procedure was performed,it is desirable that a biopsy site marker be placed in or on thepatient's body to serve as a landmark for subsequent location of thelesion.

Various types of biopsy site markers have been described, includingvisible markers applied externally to the patient's skin,radiographically (X-ray)-detectable tissue markers such as clips andstaples, and ultrasound-detectable markers, have also been described.X-ray-detectable marker wires may be inserted through a biopsy needle,leading from the surface of the patient's body to the biopsy site. Somemarkers may be biodegradable.

However, due to the consistency of breast tissue and the fact that thesebiopsy site markers are typically introduced while the breast is stillcompressed between the mammography plates, prior art biopsy markers donot always remain at the specific biopsy location after the breast hasbeen decompressed and removed from the mammography apparatus, and maysuffer from additional disadvantages as well. In order to locate anX-ray-detectable marker left at a biopsy site, an additional mammographyis generally required at the time of follow up treatment or surgery. Inaddition, once the biopsy site is located using mammography, the sitemust usually be marked again with a location wire that is visible toprovide guidance to the clinician performing the treatment or surgery.However, as the patient is removed from the mammography apparatus, orotherwise transported, the position of the location wire can change orshift before the treatment or surgery is performed, which may result intreatments being misdirected to undesired locations. Furthermore, atleast some prior art biopsy site markers can remain present at the siteof implantation for an indefinite period of time and, if not surgicallyremoved, may obscure or otherwise interfere with any subsequentmammography or imaging studies.

As an alternative or adjunct to radiographic imaging, ultrasonic imagingand visualization techniques (abbreviated as “USI”) can be used to imagethe tissue of interest at the site of interest during a surgical orbiopsy procedure or follow-up procedure. USI is capable of providingprecise location and imaging of suspicious tissue, surrounding tissueand biopsy instruments within the patient's body during a procedure.Such imaging facilitates accurate and controllable removal or samplingof the suspicious tissue so as to minimize trauma to surrounding healthytissue.

For example, during a breast biopsy procedure, the biopsy device isoften imaged with USI while the device is being inserted into thepatient's breast and activated to remove a sample of suspicious breasttissue. As USI is often used to image tissue during follow-up treatment,it may be desirable to have a marker, similar to the radiographicmarkers discussed above, which can be placed in a patient's body at thesite of a surgical procedure and which are detectable using USI.However, radiopaque markers may not be detectable with USI. A markerthat is detectable with USI enables a follow-up procedure to beperformed without the need for traditional radiographic mammographyimaging which, as discussed above, can be subject to inaccuracies as aresult of shifting of the location wire as well as being tedious anduncomfortable for the patient.

Thus, there is need in the art for biopsy site markers that aredeliverable into the cavity created by removal of the biopsy specimenand not into tissue that is located outside of that biopsy cavity, andwhich will not migrate from the biopsy cavity even when the breasttissue is moved, manipulated or decompressed. Moreover, such desiredmarkers should remain detectable at the biopsy site (i.e., within thebiopsy cavity for a desired time period); should not interfere withimaging of the biopsy site and adjacent tissues at a later time; andshould be readily distinguishable in the various imaging procedures fromlines of calcifications which frequently are signs for a developingmalignancy.

SUMMARY OF THE INVENTION

The invention is directed to materials, devices, and methods for markingintracorporeal locations such as biopsy sites for a limited time. Themarking material comprises an ultrasound-detectable bio-resorbablefinely-divided particulate material (such as a powder), in which many ofthe particles have internal cavities. Such particulate materials orpowders may be composed of particles having sizes typically less thanabout 2000 microns, and typically between about 20 microns and about2000 microns, preferably between about 20 microns and about 800 microns,more preferably between about 300 microns and about 500 microns.

The ultrasound-detectable bio-resorbable particulate materials mayinclude any bio-resorbable particulate material having cavities whichfacilitate USI. For example, the ultrasound-detectable bio-resorbableparticulate materials include particles having cavities with dimensionstypically between about 10 microns and about 500 microns, preferablyabout 20 microns to about 200 microns. The particulate materials mayalso contain binding agents. Typically, a mass of the bio-resorbableparticulate material is delivered to an intracorporeal location, such asa biopsy site within a patient. The mass of particulate material remainssituated and detectable at the biopsy site during a limited time untilit is resorbed by tissue near the biopsy site. Delivery devices havingfeatures of the invention are configured to contain the deliverable massof particles, to fit within a cannula, and to engage with a syringe.Systems for temporarily marking an intracorporeal site may include atube containing an ultrasound-detectable bio-resorbable powder, and asyringe containing a biocompatible fluid for biopsy site marking. Thetube may be configured to fit within a cannula, such as a Mammotome® orSenoCor 360™ biopsy cannula or a coaxial needle guide.

The biopsy site marker materials include powders and powder slurrieswhich can be delivered into a biopsy site cavity. Thus, much or all ofthe biopsy cavity may be filled with an ultrasound-detectable markermaterial, creating an ultrasound-detectable marker that can be as largeas the biopsy sample that was removed from the patient's body. Inaddition, this allows the ultrasound detection and definition of theboundaries of the biopsy cavity. The needle track leading to the biopsycavity may be filled as well if desired. Marker materials embodyingfeatures of the invention may be deposited at an intracorporeal locationalong with other agents, including anesthetic agents, hemostatic agents,pigments, dyes, materials detectable by magnetic resonance imaging(MRI), inert materials, and other compounds. For example, markermaterials embodying features of the invention may include radiopaquematerials as well as ultrasound-detectable materials. Such radiopaquematerial can serve to provide temporary or permanent radiographicmarking of the location. Upon deposition at a biopsy site within apatient, materials embodying features of the invention may set up or gelto form flexible or relatively rigid solid masses.

The ultrasound-detectable biopsy site markers of the present inventionprovide several advantages. A biopsy cavity with a marker materialhaving features of the present invention provides a large USI-brightmass, making it much easier, for example, to distinguish the ultrasoundsignal of the marker from signals arising naturally from within abreast. The marker materials produce bright ultrasound echo signals fromone portion of the filled region, which contrasts with the darkultrasound shadow region immediately behind the bright ultrasound echoregion. The strength of the reflected signal, and the contrast with theshadow region, make the marked site readily detectable. Such readydetectability allows, for example, lesser-experienced physicians toperform the identification by USI and the subsequent surgical resectionwithout the need for an interventional radiologist to identify and markthe biopsy cavity. These and other advantages will be further describedin the following detailed description of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an elevational view, partially in section, of a systemembodying features of the invention.

FIG. 1B is a transverse cross-sectional view of a syringe of a systemembodying features of the invention, taken along line 1B-1B shown inFIG. 1A.

FIG. 1C is a transverse cross-sectional view of a syringe of a systemembodying features of the invention, taken along line 1C-1C shown inFIG. 1A.

FIG. 1D is a transverse cross-sectional view of a tube of a systemembodying features of the invention, taken along line 1D-1D shown inFIG. 1A.

FIG. 2A is a perspective view illustrating a cubic section of a materialhaving bubble cavities (indicated with dotted lines).

FIG. 2B is a perspective view of a particle of an ultrasound-detectablebio-resorbable marker material embodying features of the invention,having enclosed bubble cavities indicated with dotted lines.

FIG. 3A is a partially cut-away, perspective view of a system asillustrated in FIG. 1 shown ready to deposit an ultrasound-detectablebio-resorbable marker material embodying features of the invention at abiopsy site within a breast of a patient.

FIG. 3B is a partially cut-away, perspective view of a system asillustrated in FIG. 3A shown in use as it deposits anultrasound-detectable bio-resorbable marker material embodying featuresof the invention at a biopsy site within a breast of a patient.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A-1D illustrate elements of a system 10 embodying features of theinvention, including a delivery tube 14 containing a quantity of anultrasound-detectable bio-resorbable particulate material 16 havingfeatures of the invention, and a syringe 18. The system 10 (includingtube 14, material 16 and syringe 18) includes an assembly 12 (whichincludes a delivery tube 14 containing a quantity ofultrasound-detectable bio-resorbable particulate material 16). In FIG.1A, an assembly 12 is shown oriented to engage with a syringe 18containing a bio-compatible fluid 20 such as sterile saline. Deliverytube 14 has a bore 22 extending from a receptacle 24 through to anoutlet 26. The quantity of ultrasound-detectable bio-resorbableparticulate material 16 is contained within bore 22. Receptacle 24 isconfigured to receive tip 28 of syringe 18 effective to form afluid-tight engagement. As illustrated in FIG. 1, tip 28 is a luer-locktip; it will be understood that other tips and locking arrangements maybe used in other embodiments of the invention. This fluid-tightengagement is able to contain fluid 20 and prevent its leakage out ofreceptacle 24 when plunger 30 is depressed, moving gasket 31 forward andforcing fluid 20 to flow out of syringe 18 and into bore 22. In bore 22the fluid 20 mixes with particulate material 16 and carries particulatematerial 16 out of tube outlet 26. Bore inner diameter 32 issufficiently large to allow ready outflow of fluid 20 and particulatematerial 16. Delivery tube outer diameter 34 is configured to be smallenough that delivery tube 14 may be readily inserted into a cannula,such as a biopsy guide cannula.

A delivery tube 14 may have indicia, such as lines or dots spaced atregular intervals along a length of the tube to indicate the tube'sposition within a cannula. A delivery tube 14 may also be configuredwith a stop, such as a bump, peg, pin, or other feature, to limit thedepth of its entrance into a cannula. In addition, a delivery tube 14may be configured to be affixed to, or lock into, a cannula so that,once introduced into the cannula, it may maintain its position for adesired period. A luer lock mechanism, a pin and slot arrangement, wherea pin on the surface of the delivery tube 14 fits into and engages witha slot on a cannula, or other mechanism or mechanisms may be used to fixthe position of a delivery tube 14 with respect to a cannula.

As illustrated in FIGS. 1A-1D, the present invention provides materialssuitable for marking intracorporeal locations, and methods and apparatusfor delivering such materials to desired intracorporeal locations. Forexample, particulate material 16 may be any ultrasound-detectable powderor other ultrasound-detectable aggregation of small particles. In someembodiments of the invention, particulate material 16 may includeradiopaque elements or materials, MRI-detectable materials, pigments,dyes, or other materials as well. System 10 and apparatus 12 may be anysystem and apparatus suitable for delivering an ultrasound-detectableparticulate material 16 to a location within a body. Any methodeffective to deliver an ultrasound-detectable particulate material issuitable for the practice of the invention.

Examples of materials, apparatus, systems, and methods embodyingfeatures of the invention are presented below. However, beforepresenting some features and embodiments illustrating the presentinvention, it is helpful to introduce some terms which are used indescribing aspects of the invention.

The term “detectable” as used herein means able to be detected by aperson, either with or without the use of imaging instrumentation (suchas ultrasound imaging instrumentation). For example, a mass or materialthat is detectable by ultrasound is able to produce a readilyrecognizable image on the display apparatus of ultrasound imaginginstrumentation. A material is “not readily detectable” within a patientif, for example, an ultrasound examination directed to the locationwhere the material had been placed does not produce a readilyrecognizable ultrasound image. As used herein, “readily” means withoutthe use of extreme or extraordinary measures or without requiringextraordinary skill.

“Bio-resorbable” as used herein means resorbable in a biologicalenvironment, such as within the body of a patient. A bio-resorbablematerial is thus a material which may be absorbed, dissolved, brokendown, degraded, assimilated, or otherwise removed from a biologicalenvironment, such as from within the body of a patient. A bio-resorbablepolymer is a polymeric material (including copolymers, alloys andpolymer mixtures composed of two or more polymers) which isbio-resorbable.

The “in-vivo lifetime” of a bio-resorbable material as used hereinrefers to the period of time after placement of the material within thebody of an animal that the material remains readily detectable. Thus,the “in-vivo lifetime” of an ultrasound-detectable bio-resorbablematerial is that period of time during which the material remainsreadily detectable within a patient by ultrasound.

The term “blowing agent” as used herein means a material or combinationof materials present during the processing or compounding of a polymermaterial that produces or breaks down into a gas at processingtemperatures or pressures. For example, where particles of polymer orcopolymer material also contains a blowing agent, and the particles areheated, extruded, or otherwise processed, the blowing agent decomposes,vaporizes, or reacts to form a gas inside the material, producingcavities within the material. A blowing agent may be a solid, a liquid(such as a liquid that vaporizes at or below the processingtemperature), or a gas. A blowing agent may be added to a material ormixture during processing, such as by directing pressurized gas into amixing chamber or a reaction chamber. Biocompatible blowing agents arepreferred.

A “bubble cavity” is an enclosed, sealed cavity within a material filledwith a gas or air. A bubble cavity may be produced by gas that ispresent in a material or mixture during processing. For example, a gasmay be present during processing where the gas has been introduced intothe processing location; or where it has been evolved or produced by thematerials present during processing; or it may have been released bymaterials present during processing. In particular, inclusion of ablowing agent during or after processing of a material or mixture ofmaterials may aid or cause the production of bubble cavities.

“Particle size” as used herein describes the external physicaldimensions of particles making up a population of small particles of amaterial, and may be determined, for example, by passing a powderthrough a sieve with a known nominal minimum passage dimension. As usedherein, a powder of a given particle size will typically includeparticles of a wide range of sizes. For example, in an aggregation ofparticles having a nominal particle size of between about 100 microns toabout 150 microns, more than about 80% of the particles (by weight) fallwithin the nominal range and up to about 20% do not. Thus, most, but notall of the particles usually fall within a nominal range described bythe particle size of a powder.

“Gelatin” as used herein means a viscous, semi-solid, or solid material,also termed a “gelatinous” material. Gelatin is typicallybiologically-derived, although synthetic gelatin is also available. Forexample, gelatin may consist largely of collagen obtained from processedanimal connective tissue. Vegetable gelatin such as agar is often madefrom kelp, algae, or other plant material. Gelatin may include bovinecollagen, porcine collagen, ovine collagen, equine collagen, agar,synthetic gelatin such as synthetic human-derived collagen, andcombinations of these.

“Bulk density” as used herein is defined as the quotient of the weightof a material, such as a powder, divided by the volume of the material.

A biocompatible liquid or fluid is a liquid that may be introduced intoa patient's body without harming the patient. Sterile saline and sterilewater containing a sugar (such as dextrose, sucrose or other sugar) orother suitable osmotically-active compounds are typical biocompatibleliquids. Other liquids, including fluids not containing water, such asbiocompatible oils, may also be used. A biocompatible liquid may bemixed with other agents or materials and used to carry contrast agents,colorants, markers, inert agents, and pharmaceutical agents into apatient.

Pharmaceutical agents, as used herein, are agents used to treat adisease, injury, or medical condition, and include, but are not limitedto, drugs, antibiotics, cancer chemotherapy agents, hormones, anestheticagents, hemostatic agents, and other medicinal compounds. Hemostaticagents are agents which tend to reduce bleeding, enhance clotting, or tocause vasoconstriction in a patient. Brachytherapy agents are typicallysources of radiation for implantation near to the site of a cancerouslesion.

In one aspect, the invention provides a bio-resorbable material suitablefor temporarily marking a biopsy site within a patient. Materialsembodying features of the invention are detectable within a patientafter introduction into a biopsy site, remain detectable for a period oftime, and then are not detectable after the period of time. Suchmaterials include bio-resorbable materials which are dissolved andabsorbed into body tissue at or near to the biopsy site. Typically, suchmaterials include a powder made from a bio-resorbable polymer such aspoly-lactic acid, poly-glycolic acid, poly-caprolactone, and copolymers,alloys, mixtures of these polymers, and combinations of these materials.

Bio-resorbable polymeric materials suitable for use in makingultrasound-detectable biopsy marker materials typically have a bulkdensity of between about 0.8 g/ml and about 1.5 g/ml. Preferably, thebio-resorbable polymeric material is a foam or other material containingcavities, with a bulk density after processing of less than about 1g/ml, more preferably between about 0.8 g/ml and about 1 g/ml.

An ultrasound-detectable marker typically must be remain in place anddetectable within a patient for at least 2 weeks to have practicalclinical value. Thus, an ultrasound-detectable marker material embodyingfeatures of the invention is detectable at a biopsy site within apatient for a time period of at least 2 weeks, preferably at least about6 weeks, and may remain detectable for a time period of up to about 20weeks, more preferably for a time period of up to about 12 weeks. Anultrasound-detectable marker material embodying features of theinvention is preferably not detectable about 6 months after placement ata biopsy site. More preferably, an ultrasound-detectable marker materialembodying features of the invention is not detectable with ultrasoundabout 12 weeks after placement at a biopsy site. A preferable in-vivolifetime for an ultrasound-detectable biopsy marker mass having featuresof the invention is between about 6 weeks and about 12 weeks.

Typically, the ultrasound-detectable biopsy marker materials of thepresent invention are deposited at locations within a patient's body toform a biopsy marker mass. Thus, for example, a quantity of powderformed from comminuted material having finely divided particles withbubble cavities within the particles may be delivered into a cavity at abiopsy site. In some embodiments, the ultrasound-detectable biopsymarker materials form a gel mass upon being introduced within the bodyof a patient. These a gel masses may be flexible gels or may be rigid,solid gels. In preferred embodiments, the marker materials remain withinthe biopsy cavity and do not migrate. The marker materials are resorbedby tissue and fluids near the biopsy site, so that, after a limitedtime, the marker materials are no longer USI-detectable at the biopsysite. The limited time during which the marker materials remainUSI-detectable is the in-vivo lifetime.

In addition, ultrasound-detectable biopsy marker materials embodyingfeatures of the invention may also include radiopaque materials orradiopaque elements, so that the biopsy site may be detected both withultrasound and with X-ray or other radiographic imaging techniques.Radiopaque materials and markers may include metal objects such asclips, bands, strips, coils, and other objects made from radiopaquemetals and metal alloys, and may also include powders or particulatemasses of radiopaque materials. Radiopaque markers may be of anysuitable shape or size, and are typically formed in a recognizable shapenot naturally found within a patient's body, such as a star, square,rectangular, geometric, gamma, letter, coil or loop shape. Suitableradiopaque materials include stainless steel, platinum, gold, iridium,tantalum, tungsten, silver, rhodium, nickel, bismuth, other radiopaquemetals, alloys and oxides of these metals, barium salts, iodine salts,iodinated materials, and combinations of these. Radiopaque materials andmarkers may be permanent, or may be temporary and not detectable after aperiod of time subsequent to their placement at a biopsy site within apatient.

In addition, ultrasound-detectable biopsy marker materials embodyingfeatures of the invention may also include MRI-detectable materials ormarkers, so that the biopsy site may be detected both with ultrasoundand with MRI or other imaging techniques. MRI contrast agents such asgadolinium and gadolinium compounds, for example, are suitable for usewith ultrasound-detectable biopsy marker materials embodying features ofthe invention. Colorants, such as dyes (e.g., methylene blue and carbonblack) and pigments (e.g., barium sulfate), may also be included inultrasound-detectable biopsy marker materials embodying features of theinvention.

Cavity-containing particles embodying features of the invention may bemade from a wide variety of biocompatible bio-resorbable material. Thus,cavity-containing particles formed from any material that is not toxic,and which is resorbable, may be used to form ultrasound-detectablebio-resorbable marker materials and compositions having features of theinvention. Some particularly suitable materials include bio-resorbablepolymers including, but not limited to, polymers of lactic acid,glycolic acid, caprolactones, and other monomers; thus, for example,suitable bio-resorbable polymers may include poly(esters), poly(hydroxyacids), poly(lactones), poly(amides), poly(ester-amides), poly(aminoacids), poly(anhydrides), poly(ortho-esters), poly(carbonates),poly(phosphazines), poly(thioesters), poly(urethanes), polyesterurethanes), polysaccharides, polylactic acid, polyglycolic acid,polycaproic acid, polybutyric acid, polyvaleric acid, and copolymers,polymer alloys, polymer mixtures, and combinations thereof.

The in-vivo lifetime of a polymeric material is related to the molecularweight of the polymer. For example, copolymers of lactic and glycolicacids having an initial molecular weight of about 60,000 daltons (60 kD)before processing, are suitable for use in making anultrasound-detectable marker material having an in-vivo lifetime ofabout 12 weeks. The starting molecular weight degrades during anextrusion process that adds gas bubbles to form bubble cavities in thepolymeric material, thereby enhancing its detectability by ultrasound.The molecular weight further degrades to about 45,000 dalton (45 kD)following gamma-ray sterilization. As is known to those of ordinaryskill in the art, other materials, including other polymeric materials,may require a different starting molecular weight in order to obtain thesame in-vivo lifetime. For example, polyglycolic acid typically degradesfaster than other materials and as such requires a substantially higherinitial molecular weight than polylactic acid or polycaprolactone toobtain a similar in-vivo lifetime.

Comminution of polymers and other starting materials (which preferablyare porous materials) by grinding, milling, pulverizing, or otherwisereducing the materials in size, is effective to form a powder.Ultrasound-detectable materials having features of the invention aretypically powders having particle sizes of about 20 microns to about2000 microns. The particles typically contain within them bubblecavities with sizes of between about 10 microns to about 500 microns.

The preferred particle size depends in one aspect on the inner diameterof a tube used to deliver the powder to a biopsy site. Larger particlesizes are more easily accommodated in larger diameter delivery tubes,while smaller delivery tubes may be used to deliver powders havingsmaller particle sizes. Where the delivery tube has an inner diameter ofno greater than about 0.075 inches (1.9 mm), powders having particlesizes of between about 20 microns and about 800 microns, and morepreferably between about 300 microns and about 500 microns, arepreferred.

The starting materials may have, or may be processed to produce, bubbleswhich produce internal bubble cavities. Comminution of the startingmaterial provides small particles with pocked, pitted, and ridgedsurfaces formed from the exposed surfaces of broken bubble cavities.Many of the particles have internal voids formed of bubble cavities.Gas-filled or air-filled bubble cavities are effective to reflectultrasound energy, and greatly enhance the ability of particlescontaining gas-filled or air-filled bubble cavities to be imageable byUSI. The sizes of such bubble cavities may be measured by lengths acrossthe cavities, through geometric centers of the cavity. Bubble cavitysize is typically between about 10 microns and about 500 microns,preferably between about 20 microns to about 200 microns.

Materials embodying features of the invention may also include bindingagents which help powder particles to adhere together and so to make thepowder a more cohesive mass. Typical binding agents include gelatin,polyethylene glycol, polyvinyl alcohol, glycerin, acrylic hydrogels suchas hydroxy ethyl methylacrylate, other organic hydrogels, and otherhydrophilic materials. Binding agents may be used singly or incombination with other binding agents. In some embodiments of theinvention, gelatin is a preferred binding agent. Gelatin suitable foruse in materials embodying features of the invention includes bovinecollagen, porcine collagen, ovine collagen, equine collagen, syntheticcollagen, agar, synthetic agar, and combinations of these. Syntheticmaterials may be preferred in order to avoid raising concerns overpossible allergies to bovine or porcine collagen. In some embodiments, amarker material includes (by weight) about one part gelatin to about twoto five parts bio-resorbable polymeric material. In a preferredembodiment, a marker material includes about one part gelatin to aboutthree to four parts bio-resorbable polymeric material (by weight)

Many properties of a marker material affect the intensity of itsultrasound reflection, including density, physical structure, molecularmaterial, and shape. For example, sharp edges, or multiple reflectingsurfaces on or within an object differing in density from itssurroundings enhances a marker's ability to be detected by ultrasound.Interfaces separating materials of different densities, such as betweena solid and a gas, produce strong ultrasound signals. The methods of thepresent invention provide marker materials effective to produce strongultrasound signals, the marker materials having gas-containing bubblecavities.

Marker materials with a high degree of porosity, whether from bubblesformed in situ during manufacture of the material, or from bubblestrapped within the material during later processing, provide strongultrasound signals when located within the body of an animal whichtranslates to improved ultrasound imaging. Starting material having gasbubbles entrained within it may be ground and sieved to obtain powdersproviding strong ultrasound signals. Portions of the powders may beselected to have particle sizes within a desired size range.

A cubic section of a material having internal bubble cavities isillustrated in perspective view in FIG. 2A. Internal bubble cavities 36are indicated by dotted lines. Comminution (i.e., grinding, pulverizing,or otherwise reducing to small particles) of such a material intoparticles containing bubble cavities produces an ultrasound-detectablematerial suitable for marking an intracorporeal location. The particlesresulting from such comminution form an aggregation (which may be termeda powder) which may be deposited within a body. An illustration of onesuch particle is shown in FIG. 2B, which is at a smaller scale than FIG.2A.

Gas bubbles can be introduced into a material by whipping a gas into thematerial during processing of a material, by release of gas from withinthe material, or by directing a gas into a material. Alternatively,bubbles within a material may be created by secondary processing such asextruding a polymer and a blowing agent together to create a rod havinggas bubbles entrained within it. A blowing agent may decompose torelease a gas, or may react with other materials to form a gas. Forexample, a blowing agent that breaks down into a gas at elevatedprocessing temperatures or pressures may be included in a mixture inorder to produce bubbles within a material. The material produced afterintroduction of such bubbles is one riddled with bubble cavities,forming a foam or sponge-like structure.

Blowing agents suitable for practicing the methods of the inventioninclude, but are not limited to, sodium bicarbonate, ammonium carbonate,and other carbonates; sodium boron hydride, silicon oxy-hydride, andother hydrides; hydrochlorofluorocarbon compounds, andchlorofluorocarbon compounds. Liquid blowing agents, such ashydrocarbons and alcohols, may also be used. For example, for polymershaving molecular weights of up to about 60 kD, liquid blowing agents,particularly hydrocarbons and alcohols having boiling points in therange of between about 75° C. and about 95° C., are suitable for thepractice of the invention. Such blowing agents include, but are notlimited to, hexane, heptane, heptene, propyl alcohol, isopropyl alcohol,other hydrocarbons and alcohols, and mixtures of hydrocarbons andalcohols. Biocompatible blowing agents are preferred blowing agents.

Sodium bicarbonate is a presently preferred blowing agent; it has abroad and relatively low decomposition temperature well within theprocessing parameters of typical bio-resorbable polymeric materials.Mixtures of sodium bicarbonate and polymeric material usually includeless than about 10% by weight sodium bicarbonate, and typically includeno greater than about 5% sodium bicarbonate by weight. In a preferredembodiment of the methods of the present invention, about 2% by weightsodium bicarbonate is combined with polylactic acid and polyglycolicacid copolymer, and the combination is extruded to form a rod.

Mixtures of polymers such as polylactic acid, polyglycolic acid,polycaprolactone, their co-polymers, and the like, with about 2% byweight of a blowing agent such as sodium bicarbonate, produce gasbubbles that vary in size between about 10 microns and about 500microns, preferably about 20 microns to about 200 microns, with mostbubbles averaging about 100 microns in size. The bubbles are typicallynot spherical in shape, but are generally elongated and distorted, dueto the shear applied to the material as it moves though the extrusiondie and due to the tension applied to the material in its plastic state.The exterior of rods extruded during processing is typically found to bebumpy. This surface texture is produced as a result of the bubbles beingdistorted from this process as well as surface bubbles swelling andbursting as the pressure is relieved from within the extrusion meltchamber.

The bulk density of raw polymeric material suitable for the practice ofthe invention is typically about 1.3 g/ml before processing. A preferredraw polymeric material is a mixture of polylactic acid (PLA) andpolyglycolic acid (PGA) in a ratio of 65% to 35% (PLA:PGA) by weight.The bulk density of the processed material can be varied from about 0.8g/ml to about 1.5 g/ml to obtain a material which has the desiredultrasound characteristics. This variation can be obtained by increasingthe proportion of blowing agent in the mix (for example, up to about0.5% sodium bicarbonate by weight), by processing the extrusion at ahigher temperature, or both. A lower bulk density material may beproduced by either variation of the method (i.e., by increasing blowingagent or increasing extrusion temperature). The effect of lowering thedensity of the processed material is to increase the fragility of theextruded rod, to reduce the amount of material required, and to reduceits in-vivo lifetime.

Inclusion of excessive amounts of blowing agent (e.g., typically greaterthan about 10% by weight in PLA:PGA mixtures) tended to produceprocessed material that was mostly gas surrounded by very thin layers ofpolymer. Such material was not as suitable for use in anultrasound-detectable biopsy site marker material as more densematerials. These materials produced with excessive amounts of blowingagent had relatively thin polymer structures that degraded more rapidlythan thicker structures, and also tended to lose gas from the bubblecavities, which then tended to collapse so that the desirable ultrasoundcharacteristics of the material was lost. Lower amounts of blowing agent(e.g., less than about 10%, preferably not greater than about 5%, morepreferably about 2%, blowing agent by weight included with polymers andcopolymers of polylactic acid, polyglycolic acid, and polycaprolactone)so as to provide material having a bulk density of about 0.8 g/ml toabout 1.5 g/ml, preferably about 1.0 g/ml or less, provided materialshaving the desired ultrasound signal properties and the desired in-vivolifetime.

A binding agent can be added to the marker material to make the powder amore cohesive mass. Materials such as porcine gelatin, bovine gelatin,polyethylene glycol, polyvinyl alcohol, glycerin, or other hydrophilicmaterial are suitable for use in materials having features of theinvention. One desirable characteristic of binding agent materials is tokeep the powder from dispersing away from the biopsy site followingdelivery at the biopsy site. In general, the amount of binding agent ismuch less than the amount of ultrasound-detectable bio-resorbablepowder. For example, a suitable mixture is one part porcine gelatin to 3parts bio-resorbable ultrasound visible powder.

A typical human breast has a substantial number of features that arevisualized with ultrasound. These features all have characteristicsignals. Fibrous tissue or ligaments tend to show up as bright streaks,fat seems to appear as a dark gray area, the glandular tissue appears asa mottled medium gray mass. Cancerous lesions typically appear as adarker area with a rough outer edge which has reduced throughtransmission of the ultrasound energy.

However, due to the large amount of fibrous tissue normally present in ahuman breast, and due to the presence of ligaments running through thebreast, a marker that simply has a bright signal alone will not providea useful signal that can is readily discernable from the many anatomicfeatures normally present within a human breast. Such markers aretypically small, being sized to fit within a syringe or other deliverytube, and so are often not readily distinguishable from natural featuresof the breast, which include occasional small ultrasound-bright spots.One advantage of the ultrasound-detectable biopsy marker materials ofthe present invention is that the materials provide an ultrasound signalwhich can be readily differentiated from anatomic structures within thebreast, so that the identification and marking of a biopsy cavity doesnot require extensive training and experience.

The gas bubbles within the materials processed as described herein formbubble cavities within the material that create a bright (white) mark orsignal when viewed with ultrasound, enhancing the strength of theultrasound signal intrinsic to the polymeric material itself. The roughedges of fractured or partial cavities may also help to enhance theultrasound image. In addition to providing a strong ultrasound signal,the gas bubbles also effectively stop transmission of the ultrasoundsignal, creating a shadow behind the bright spot.

FIG. 2B is a perspective view of a particle of an ultrasound-detectablebio-resorbable marker material embodying features of the invention,having an enclosed bubble cavity 36 indicated with dotted lines. Thesurface of the particle illustrated in the figure is irregular, havingcurved indentations, rounded features, and jagged edges. Particles ofultrasound-detectable finely-divided particulate materials havingfeatures of the invention have a variety of shapes and surface features,not all particles having the same shapes and features. Many, preferablya majority, of the particles of ultrasound-detectable finely-dividedparticulate materials having features of the invention include at leastone bubble cavity. The bubble cavity may be of any size or shape. Thesize of a bubble cavity may be determined by measuring a distance alonga line passing between one surface of the cavity, through a geometriccenter of the cavity, to another surface of the cavity. Preferably, mostbubble cavities have a size between about 10 microns and about 500microns, more preferably between about 50 microns and about 200 microns.

The biopsy marker materials of the present invention includeultrasound-detectable bio-resorbable particulate material and may alsoinclude a biocompatible fluid vehicle which helps to carry the powder tothe biopsy site. When deposited at a cavity at an intracorporeallocation, the ultrasound-detectable marker material, with or without acarrier fluid, is able to fill the entire cavity. For example, where thecavity is a biopsy cavity left after removal of a biopsy sample from abreast, the size of the ultrasound-detectable marker can be as large asthe biopsy sample that was removed from the breast, which makes it mucheasier to distinguish the ultrasound signal of the marker from signalsarising naturally from within a breast.

Thus, the ultrasound-detectable biopsy site marker materials of thepresent invention provide several advantages over prior markers. Forexample, the gas bubbles and bubble cavities within the material show upas a bright spot which allow for it to be distinguished from backgroundanatomy. At the same time, the gas bubbles and bubble cavities produce ashadow below the bright spot. Thirdly, filling a biopsy cavity with theultrasound marker outlines the entire biopsy site. When used with aMammotome® or SenoCor 360™ biopsy, the marker mass creates a largecurved bright upper surface which matches the outline of the biopsycavity, and a shadow below this surface.

Ultrasound-detectable biopsy marker materials having features of thepresent invention may be made by any suitable method, including themethods described below. For example, ultrasound-detectable biopsymarker materials having features of the present invention may be made byreducing a bio-resorbable material having bubble cavities to a powder. Amaterial may be reduced to a powder by granulating it, as by grindingthe material, chopping the material, subjecting the material to theimpact of a hard tool, impacting the material onto a hard surface,agitating the material, or by other methods known in the art. Thestarting material may include colorants, contrast agents, and othermaterials if desired.

Cryogrinding is a suitable method of comminuting a material to producebio-resorbable ultrasound-detectable marker materials having features ofthe invention. A starting block of material may be frozen, for exampleby exposure to a liquified gas such as liquid nitrogen, and then poundedor beaten to shatter the block into smaller pieces, which may then beground between grinding plates to reduce the pieces to a desiredparticle size.

Comminution of the material is continued until a powder having aparticle size of less than about 2000 microns is produced. Preferably,the comminution is effective to provide a powdered biopsy markermaterial having a particle size of between about 20 microns and about800 microns, more preferably between about 300 microns and about 500microns. Typically, the resulting powder flows freely when poured. Itmay be stored as a dry powder. Powdered pigment, contrast agent, orother particulate material may also be included at this stage ifdesired.

Granulation and powdering typically produce a wide range of particlesizes. A method of selecting particles of a desired size is to pass thepowdered material through a sieve. For example, a powder resulting fromgranulation may be loaded onto a sieve having a desired sieve size, andparticles collected from beneath the sieve after passing through thesieve. This will separate the powder into two portions: a first portionretained by, the sieve, and thus apparently unable to pass through it,and a second portion that has passed through the sieve. The secondportion that has passed through the sieve consists of particles havingparticle sizes less than the sieve size of the sieve. Thus, for example,a powder having a particle size of less than about 2000 microns may becollected by passing a powder through a sieve having a sieve size of2000 microns, and a powder having a particle size of less than about 800microns may be collected by passing a powder through a sieve having asieve size of 800 microns.

Multiple sieves may be used in a conventional fashion to separate thepowder into different size particle portions. For example, passing apowder through a first sieve with a larger sieve size, and then passingthe resulting powder through a second sieve having a smaller sieve sizecan separate out a powder portion having particle sizes falling betweenthe first sieve size and the second sieve size.

In preferred embodiments, the bio-resorbable material is abio-resorbable polymeric material. Suitable polymeric materials includepolylactic acid, polyglycolic acid, polycaprolactone, and combinationsof these polymers. Polymeric mixtures may include copolymers and alloysof bio-resorbable polymers. The bio-resorbable material or materialsused to make ultrasound-detectable biopsy site marker materials havingfeatures of the present invention preferably have bubble cavities. Oneway to characterize bubble cavities is to describe the cavity size,which is defined by an average length of a population of, cavities in amaterial. Where only a portion of what once was a larger bubble cavityremains, cavity size is measured by a length spanning the existingportion of the cavity. Cavity size may be measured, for example, byexamination of the material with an optical microscope, preferably usingan eyepiece with a reticle, or by inspection of electron micrographs ofspecimens of a material. Materials suitable for the practice of theinvention have a cavity size of about 2000 microns or less. Preferredmaterials have a cavity size of between about 10 microns and about 500microns, more preferably the cavity size is between about 20 microns andabout 200 microns.

Bubble cavities may be introduced into a material during processing byany suitable method. For example, bubble cavities may be introduced intoa polymeric material by whipping a gas into a polymeric material whilethe material is heated and in a plastic or malleable state. Gas may beintroduced by providing a source of high pressure gas, such as nitrogenor argon, and directing the gas into a mixing chamber containing heatedpolymeric material.

Another suitable method for providing a material having bubble cavitiesis to mix a material and a blowing agent, preferably a biocompatibleblowing agent, and to extrude the material and a blowing agent together.For example, extrusion of a polymeric material and a blowing agent willcreate a polymeric rod having gas bubbles entrained within it. Thesebubbles will typically not have a spherical shape, but instead may beelongated or irregular, due to the shear forces experienced duringextrusion. Thus, for example, an ultrasound-detectable biopsy markermaterial may be made by extruding a polymeric material and a blowingagent to provide a bio-resorbable polymeric material having bubblecavities, and then reducing the material to a powder. Typically, amixture of polymer and blowing agent should include less than about 10%by weight of the blowing agent, preferably no more than about 5%, mostpreferably about 2%. Suitable blowing agents include sodium bicarbonate,ammonium carbonate, sodium boron hydride, silicon oxy-hydride,hydrochlorofluorocarbon compounds, chlorofluorocarbon compounds,mixtures of sodium bicarbonate, ammonium carbonate, sodium boronhydride, silicon oxy-hydride, hydrochlorofluorocarbon compounds, andchlorofluorocarbon compounds, hexane, heptane, heptene, propyl alcohol,isopropyl alcohol, other hydrocarbons and alcohols, and mixtures ofhydrocarbons and alcohols.

Sodium bicarbonate is a preferred blowing agent. In one embodiment ofthe methods of the invention, an ultrasound-detectable biopsy markermaterial may be made by extruding a copolymer of poly-lactic acid andpoly-glycolic acid with sodium bicarbonate. The amount of sodiumbicarbonate should make up less than about 10%, and preferably not morethan about 5%, of the total starting material weight. More preferablysodium bicarbonate makes up about 2% of the total starting materialweight of the mixture.

Alternative methods of making a material having cavities are alsosuitable. For example, a powder of material dissolvable in water orother solvent may be mixed into a polymer matrix to create a polymerencapsulating the dissolvable powder, and the polymer matrix containingthe powder then exposed to the solvent. The solvent dissolves the powderout of the polymer matrix, leaving cavities, thus creating a porouspolymer. Suitable powder materials for use in practicing this methodinclude salts such as sodium chloride, potassium chloride, calciumchloride and other salts, sugars such as glucose, sucrose, and otherwater-soluble sugars, and the like. Comminution of the polymer matrixmay be performed either before or after dissolving out the powder;preferably, comminution of the polymer matrix is performed afterdissolution of the encapsulated powder.

Similarly, a slurry can be made of a dispersion of a polymer (whichcould also be a copolymer, polymer alloy, polymer mixture, orcombination of these) and a dissolvable powder (such as a salt or asugar, as described above). The slurry can be cast to provide a solidmaterial of polymer with dissolvable powder inclusions, and the powderthen dissolved by exposing the cast material to a solvent. Theinclusions need not be solid; an emulsion made up of a polymer (whichcould also be a copolymer, polymer alloy, polymer mixture, orcombination of these) and a non-miscible liquid can be cast to provide asolid with included droplets of the non-miscible liquid. Thenon-miscible liquid may then be extracted so that the solid materialbecomes a foam. For example, a non-miscible liquid may be extracted byexposing the cast material to low pressure, or by freeze-drying the castmaterial in a low-temperature, low pressure environment, allowing thenon-miscible liquid to escape from the cast material by diffusion.

In addition, an ultrasound-detectable biopsy marker material havingfeatures of the present invention may include a binding agent with thepowder. A binding agent helps to keep the powder together duringdeposition at a biopsy site. Suitable binding agents include gelatin,polyethylene glycol, polyvinyl alcohol, glycerin, other hydrophilicmaterials, and combinations of these. Suitable gelatins include bovinecollagen, porcine collagen, ovine collagen, equine collagen, syntheticcollagen, agar, synthetic gelatin, and combinations of these.

Biopsy site marker materials having features of the present inventionmay be delivered to a biopsy site in dry form, or in wet form, as in aslurry or suspension. Pressure may be applied to the powder in order toeject it from a storage location, such as a delivery tube. Pressureeffective to deliver an ultrasound-detectable bio-resorbable markermaterial having features of the invention includes gas pressure,acoustic pressure, hydraulic pressure, and mechanical pressure. Forexample, dry ultrasound-detectable bio-resorbable powders may be blowninto a biopsy site by the action of gas pressure from a pressurized gasdirected behind or alongside the powder and towards the biopsy site.Such gas pressure may be supplied by carbon dioxide or nitrogen gascontained within a pressure vessel under high pressure, and the pressurereleased into a chamber containing a dry ultrasound-detectablebio-resorbable powder effective to drive the powder through an attachedneedle or catheter having an orifice within a biopsy site.Alternatively, a syringe filled with air or other gas may be connectedto a tube or chamber containing an ultrasound-detectable bio-resorbablepowder and the syringe plunger depressed so as to force the air or gas,and the powder, through a needle or catheter attached to the tube orchamber and having an orifice within a biopsy site. It will beunderstood that any device for providing gas or liquid flow through adelivery tube containing an ultrasound-detectable bio-resorbable powderis suitable to deliver a bio-resorbable marker mass to a desiredlocation within a patient's body.

Mechanical pressure may be delivered by, for example, direct contactwith a plunger. Where the particle size is significant relative to thediameter of a delivery tube, an ultrasound-detectable bio-resorbablepowder having features of the invention may be expelled from the tube bydirectly pushing on it with a plunger. Thus, for example, where theparticle size of such a powder is within a range of between about 60% toabout 90% of the inner diameter of the delivery tube bore, a quantity ofpowder within the delivery tube may be expelled by direct action of aplunger on the powder without need for liquid or gas. Alternatively,acoustic pressure supplied by, for example, an ultrasound transducer,may be used to deliver an ultrasound-detectable bio-resorbable powderhaving features of the invention.

A preferred method for delivering an ultrasound-detectablebio-resorbable powder to a biopsy site utilizes a biocompatible liquidto drive or carry the powder into the biopsy cavity at the biopsy site.For example, a quantity of ultrasound-detectable bio-resorbable powdermay be contained within a tube or chamber that leads directly orindirectly to a biopsy site. The powder may be dispensed by theapplication of hydraulic pressure applied by a syringe containingsterile saline or other suitable liquid. Flow of the liquid carries thepowder into the biopsy site; turbulence acts to mix the dry powder withthe liquid to provide a slurry or suspension and to provide a fairlyuniform distribution of the powder throughout the biopsy cavity. Thesyringe is preferably configured to tightly engage with the tube orchamber, in order to prevent leakage and to insure sufficient pressureand flow is directed towards the biopsy site. The tube or chambercontaining the ultrasound-detectable bio-resorbable powder may be anelongated hollow tube, having a bore completely filled with the powder;or an elongated hollow tube, having a bore partially filled with thepowder; or a chamber having internal dimensions that change along thelength, configured to hold a desired quantity of ultrasound-detectablebio-resorbable powder and to provide a desired amount of mixing with thefluid.

In a most preferred embodiment, the quantity of ultrasound-detectablebio-resorbable powder is contained within a tube termed a “deliverytube.” The tube has an outside diameter that is sized to fit within acannula, such as a Mammotome® or SenoCor 360™ cannula. For example, asuitable delivery tube has an outside diameter (OD) of about 0.096inches and has an inner diameter (ID) of about 0.074 inches. Other sizesare also suitable, the exact dimensions depending on the biopsy deviceused. In addition, a delivery tube may have markings to aid indetermining the depth of the tube within a cannula, surface features(such as pins, slots, bumps, bars, wedges, luer-lock fittings, or bands,including a substantially conical circumferential band) effective tocontrol the depth into which a delivery tube is fitted within a cannulaor effective to lock a delivery tube into position within a cannula. Forexample, a delivery tube may have pins or bumps configured to engage aslot or a leading edge of a cannula, or a luer-lock fitting configuredto lock into a cannula.

A cannula may also be configured to receive and to engage a deliverytube. A cannula may have pins, slots, wedges, bumps, bands, luer-lockfittings, or the like, to engage a delivery tube and to hold it into adesired position within the cannula. For example, a cannula may have aluer-lock fitting, or a slot to engage a pin on a delivery tube, or aninternal bump wedge or band that limits the distance of travel of thedelivery tube within the cannula.

Delivery tubes embodying features of the present invention may be madeof any suitable bio-compatible material. Preferably, the material hassufficient strength to withstand the hydraulic pressure required todispense the material (typically greater than 100 psi) and is able to besterilized. A polyether block amide such as a Pebax®, preferably a 72Durometer Pebax®, is one example of a suitable material. Hydraulicpressure may be supplied by depressing the plunger of a syringe, such asa 1 to 3 cc syringe, containing a suitable fluid and connected to thedelivery tube. The amount of material required within the delivery tubewill vary depending on the biopsy cavity size. Typically, quantities ofbetween about 0.2 to about 1.2 ml of powder will be required. In manycases, a quantity of about 0.5 ml of the powder is suitable.

The delivery tube can be sized to accept any volume desired to beinjected into the biopsy cavity. The average Mammotome® biopsy removesabout 1 ml of tissue. The present inventors have found that about 0.5 mlof dry powder works best to fill such a biopsy cavity with the powderand fluid. Use of more powder typically leads to some filling of theneedle track as well as of the cavity at the biopsy site. Smallervolumes of powder may be used for smaller cavities at a biopsy site,such as are created with an automated Tru-Cut® biopsy or a singleSenoCor 360™ biopsy, available from SenoRx, the assignee of the presentinvention.

Ultrasound-detectable bio-resorbable powder may be loaded into andelivery tube in preparation for use in marking a biopsy site. Thedelivery tube may be attached to a syringe having about 0.5 ml to about2 ml of fluid, preferably about 1.0 ml to about 1.5 ml of fluid, at anysuitable time before delivery to a biopsy site. After a biopsy has beentaken from a biopsy site within a patient, the delivery tube is placedwith its distal end at or directed to the biopsy site, typically byplacing the delivery tube within a cannula leading to the biopsy site,and the powder is then dispensed by directing the fluid through thedelivery tube, so that it is thereby deposited at the biopsy site.

Alternatively, a syringe could be loaded with an ultrasound-detectablebio-resorbable powder having features of the invention, filled with abiocompatible fluid, and then shaken or stirred to create a slurry. Thesyringe may then be connected to a delivery tube or catheter, and theslurry injected through the delivery tube or catheter to fill the biopsysite with an ultrasound-detectable bio-resorbable marker composition.

When mixed with a suitable fluid, ultrasound-detectable bio-resorbablepowders having features of the invention may form a suspension, whichmay be dilute or concentrated, depending on the relative amounts offluid and of powder. A concentrated suspension may be termed a slurry,and may be somewhat viscous and have the consistency of a paste. Theconsistency of the suspensions may change with time; for example, asuspension of an ultrasound-detectable bio-resorbable powder havingfeatures of the invention may set up over time to form a semi-solid gel.Inclusion of a binding agent such as gelatin, preferably an amount ofgelatin of about 5% to about 50% by weight, is effective to help gelformation after mixing an ultrasound-detectable bio-resorbable powderwith a suitable fluid. Gelatin typically hardens to its ultimatefirmness within minutes at normal body temperature.

The fluid used to deposit the powder at a biopsy site may contain otheragents, including inert agents, osmotically active agents,pharmaceutical agents, and other bio-active agents. For example, asuitable biocompatible liquid may be selected from the group consistingof sterile saline, sterile saline containing a pharmaceutical agent,sterile saline containing an anesthetic agent, sterile saline containinga hemostatic agent, sterile saline containing a colorant, sterile salinecontaining a radio contrast agent, sterile sugar solution, sterile sugarsolution containing a pharmaceutical agent, sterile sugar solutioncontaining an anesthetic agent, sterile sugar solution containing ahemostatic agent, sterile sugar solution containing a colorant, sterilesugar solution containing a radio contrast agent, biocompatible oils,biocompatible oils containing a pharmaceutical agent, biocompatible oilscontaining an anesthetic agent, biocompatible oils containing ahemostatic agent, biocompatible oils containing a radio contrast agent,and biocompatible oils containing a colorant. For example, anestheticagents may be beneficial by reducing patient discomfort.

Hemostatic agents tend to reduce bleeding, enhance clotting, or to causevasoconstriction in a patient. Hemostatic agents include adrenochrome,algin, alginic acid, aminocaproic acid, batroxobin, carbazochromesalicylate, cephalins, cotarmine, ellagic acid, epinephrine,ethamsylate, factor VIII, factor IX, factor XIII, fibrin, fibrinogen,naphthoquinone, oxamarin, oxidized cellulose, styptic collodion,sulamrin, thrombin, thromboplastin (factor III), tolonium chloride,tranexamic acid, and vasopression.

Pharmaceutical agents are often used to promote healing, and to treatinjury, infection, and diseases such as cancer, and may includehormones, hemostatic agents and anesthetics as well as antibacterial,antiviral, antifungal, anticancer, and other medicinal agents.Pharmaceutical agents may be included as part of anultrasound-detectable bioresorbable material placed within a biopsycavity in order, for example, to promote healing, prevent infection, andto help treat any cancer cells remaining near the biopsy site.

Thus, pharmaceutical agents which may be included with a fluid or with apowder to form an ultrasound-detectable bioresorbable material havingfeatures of the invention include, but are not limited to: penicillins,cephalosporins, vancomycins, aminoglycosides, quinolones, polymyxins,erythromycins, tetracyclines, streptomycins, sulfa drugs,chloramphenicols, clindamycins, lincomycins, sulfonamides, paclitaxel,docetaxel, acetyl sulfisoxazole, alkylating agents, antimetabolites,plant alkaloids, mechlorethamine, chlorambucil, cyclophosphamide,melphalan, ifosfamide, methotrexate, 6-mercaptopurine, 5-fluorouracil,cytarabine, vinblastine, vincristine, etoposide, doxorubicin,daunomycin, bleomycin, mitomycin, carmustine, lomustine, cisplatin,interferon, asparaginase, tamoxifen, flutamide, amantadines,rimantadines, ribavirins, idoxuridines, vidarabines, trifluridines,acyclovirs, ganciclovirs, zidovudines, foscarnets, interferons,prochlorperzine edisylate, ferrous sulfate, aminocaproic acid,mecamylamine hydrochloride, procainamide hydrochloride, isoproterenolsulfate, phenmetrazine hydrochloride, bethanechol chloride, methacholinechloride, isopropamide iodide, tridihexethyl chloride, phenforminhydrochloride, methylphenidate hydrochloride, theophylline cholinate,cephalexin hydrochloride, diphenidol, meclizine hydrochloride,prochlorperazine maleate, phenoxybenzamine, thiethylperzine maleate,anisindone, diphenadione erythrityl tetranitrate, isofluorophate,acetazolamide, methazolamide, bendroflumethiazide, chloropromaide,tolazamide, chlormadinone acetate, phenaglycodol, allopurinol, aluminumaspirin, hydrocortisone, hydrocorticosterone acetate, cortisone acetate,dexamethasone and its derivatives such as betamethasone, triamcinolone,methyltestosterone, 17-S-estradiol, ethinyl estradiol, ethinyl estradiol3-methyl ether, prednisolone, 17-hydroxyprogesterone acetate compounds,19-nor-progesterone, norgestrel, norethindrone, norethisterone,norethiederone, progesterone, norgesterone, norethynodrel, aspirin,indomethacin, naproxen, fenoprofen, sulindac, indoprofen, nitroglycerin,isosorbide dinitrate, propranolol, timolol, atenolol, alprenolol,cimetidine, clonidine, imipramine, dihydroxyphenylalanine, theophylline,calcium gluconate, ketoprofen, ibuprofen, cephalexin, haloperidol,zomepirac, ferrous lactate, vincamine, diazepam, phenoxybenzamine,milrinone, capropril, mandol, quanbenz, hydrochlorothiazide, ranitidine,flurbiprofen, fenufen, fluprofen, tolmetin, alclofenac, mefenamic,flufenamic, difuinal, nizatidine, sucralfate, etintidine, tetratolol,minoxidil, chlordiazepoxide, diazepam, amitriptyline, imipramine,prostaglandins, coagulation factors, analogs and derivatives of thesecompounds, and pharmaceutically acceptable salts of these compounds, ortheir analogs or derivatives.

Some possible components and combinations of components suitable for usein ultrasound-detectable bio-resorbable marker materials having featuresof the invention are presented in the following table. Comments arepresented regarding the effects of including either a low percentage ora high percentage of the indicated components in a material made up of amixture of components.

TABLE Low Percentage in High Percentage in Component Function theMixture the Mixture Bio-resorbable Ultrasound marker Lightens theIncreases the polymer with predetermined in- ultrasonic contrast,ultrasound contrast to vivo lifetime creating a more USI create aUSI-opaque translucent image of image of the filled the filled cavitycavity Binding agent Reduces settling or Forms a thinner slurry Forms athicker slurry particulate which makes delivery which doesn't easilysegregation into the biopsy cavity displace from the easier; may alsohelp biopsy cavity control the relative density of the ultrasound markerRadiographic marker Permanent Not present - no Provides permanentmaterial or objects radiographic biopsy- radiographic markingradiographic marking site marker Biocompatible fluid Aids in deliveringThicker slurry, which Thinner slurry, makes particulate mass and doesn'teasily deposition into cavity in forming a slurry displace from cavityeasier; may also help control the relative density of ultrasoundcontrast agent Hemostatic agent Stops bleeding inside Stops lightbleeding Stops heavy bleeding cavity Anesthetic Controls pain duringControls pain during Controls pain during and after procedure procedureand after procedure Radiographic contrast Defines size, shape, Providelight amount Provide dense agent boundaries of biopsy of radiopacitywithin radiopacity within cavity for radiographic cavity; transient incavity; transient in imaging nature nature Colorant Visual cavitymarking Little or no visual Dark visual marking of marking of cavitycavity

An assembly for delivering an ultrasound-detectable bio-resorbablepowder includes an delivery tube configured to be received within abiopsy guide cannula. Such a delivery tube is also configured to engagea syringe, and to hold a quantity of ultrasound-detectablebio-resorbable powder. The delivery tube may be configured to hold aquantity of ultrasound-detectable bio-resorbable powder by having aninner volume of between about 0.2 ml and about 1.2 ml, preferablybetween about 0.5 ml and about 1.0 ml. A delivery tube having featuresof the invention may also be configured to fit within a biopsy guidecannula, such as a Mammotome® guide cannula, a SenoCor 360™ cannula, ora Tru-Cut® cannula. For example, a delivery tube having an outsidediameter less than about 0.1 inch (2.54 mm) is able to fit within aMammotome® guide cannula. In addition, a delivery tube having featuresof the invention may also be configured to sealingly engage with asyringe, that is, to form a strong, water-tight connection. An exampleof a suitable connection is a luer-lock connection configured tosealingly engage with a syringe.

In further embodiments of the invention, a system for temporarilymarking a biopsy site within a patient is provided. Such a systemincludes a syringe; a supply of ultrasound-detectable bio-resorbablepowder; and a delivery tube configured to engage the syringe.Preferably, the engagement between the syringe and delivery tube iswater-tight engagement, and is sufficiently strong as to withstand thehydraulic pressure generated by depressing the syringe plunger anddirecting fluid within the syringe through the delivery tube effectiveto deposit ultrasound-detectable bio-resorbable powder at the biopsysite. The supply of ultrasound-detectable bio-resorbable powder may bein a packet, a syringe, a delivery tube, or other container. Inpreferred embodiments of the system, the supply of ultrasound-detectablebio-resorbable powder is located within the delivery tube. The deliverytube is preferably configured to be received within a biopsy guidecannula. In more preferred embodiments, the delivery tube has an outsidediameter of less than about 0.1 inch (2.54 mm). The system may furtherinclude a supply of biocompatible liquid, which is preferably sterilesaline. More preferably, the biocompatible liquid is contained withinthe syringe of the system for ease of use and to avoid the possibilityof spillage or contamination.

FIG. 3A is a partially cut-away perspective view of a system 10 asillustrated in FIG. 1, shown ready to deposit an ultrasound-detectablebio-resorbable powder 16 within a cavity 46 at a biopsy site 38. FIG. 3Bshows the system, following depression of plunger 30, as it deposits anultrasound-detectable bio-resorbable marker material 50 embodyingfeatures of the invention (which includes ultrasound-detectablebio-resorbable powder 16 mixed with fluid 20) at a biopsy site 38 withina breast 40 of a patient.

An incision 42 in the breast allows access to biopsy site 38. Biopsyguide cannula 44 extends through incision 42 into cavity 46 at biopsysite 38. Syringe 18, containing a bio-compatible fluid 20, is tightlyengaged with a delivery tube 14, which extends within guide. cannula 44so as to locate delivery tube outlet 26 within biopsy site cavity 46.Delivery tube outer diameter 34 is configured to allow delivery tube 14to fit inside the inner diameter 48 of biopsy guide cannula 44. Markings52 (shown in FIG. 3A) spaced at regular intervals along the outersurface of delivery tube 14 indicate the depth of insertion of the tubewithin the cannula and aid in the proper placement of delivery tubeoutlet 26 into position within cavity 46. Depression of plunger 30forces fluid 20 out of syringe 18 through delivery tube 14, where fluid20 mixes with and carries ultrasound-detectable bio-resorbable powder 16out of delivery tube outlet 26 to deposit ultrasound-detectablebio-resorbable biopsy site marker material 50 within cavity 46 at biopsysite 38. As shown in FIG. 3B, an optional locking mechanism 54,including pin 56 (on delivery tube 14) configured to engage with slot 58(on cannula 44) may be used to fix delivery tube 14 in position withincannula 44 and to help prevent movement of delivery tube outlet 26relative to cannula 44 when plunger 30 is depressed.

What is claimed is:
 1. A marking system, comprising: a delivery tube;and an ultrasound-detectable biopsy marker carried by the delivery tube,the ultrasound-detectable biopsy marker formed of particles of materialhaving internal bubble cavities, wherein a particle size of theparticles is between about 200 microns and about 500 microns, and thebubble cavities have a size of at least 50 microns, wherein the bubblecavities have geometric centers and the bubble cavity size is measuredby length through the geometric centers of the bubble cavities.
 2. Amarking system, comprising: a delivery tube; and anultrasound-detectable biopsy marker carried by the delivery tube, theultrasound-detectable biopsy marker formed of particles of materialhaving internal bubble cavities and having a particle size between about200 microns and about 800 microns, the bubble cavities having a size ofat least 50 microns, wherein the bubble cavities have geometric centersand the bubble cavity size is measured by length through the geometriccenters of the bubble cavities.
 3. The marking system of claim 2,wherein at least a portion of the particles have both internal bubblecavities and have exposed surfaces of broken bubble cavities.
 4. In amarking system for delivering a marker mass, the marker mass comprisingan ultrasonically detectable powder detectable in-vivo within apatient's biopsy site for a period of at least two weeks but not longerthan six months, the ultrasonically detectable powder having particleswith a particle size of about 200 to about 800 microns and the particleshaving one or more bubble cavities within the particles smaller than theparticle size of the particles, wherein the ultrasonically detectablepowder comprises about 65% by weight polylactic acid and about 35% byweight polyglycolic acid.
 5. In a marking system for delivering a markermass, the marker mass comprising an ultrasonically detectable powderdetectable in-vivo within a patient's biopsy site for a period of atleast two weeks but not longer than six months, the ultrasonicallydetectable powder having particles with a particle size of about 200 toabout 800 microns and the particles having one or more bubble cavitieswithin the particles smaller than the particle size of the particles,and comprising one part gelatin and about five parts comminutedbio-resorbable polymeric material, the particles of the comminutedmaterial having bubble cavities of about 50 to about 200 microns insize.